Reduction of surface oxidation during electroplating

a technology of surface oxidation and electroplating, which is applied in the direction of liquid/solution decomposition chemical coating, chemical vapor deposition coating, solid/suspension decomposition chemical coating, etc. it can solve the problems of long-term solderability, difficult to achieve 3, and reduce the solderability of tin or tin alloy deposits, so as to enhance the long-term solderability of metal deposits, reduce surface oxide formation, and reduce surface oxide formation

Inactive Publication Date: 2006-01-26
TECHNIC INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The incorporation of phosphorus significantly reduces surface oxidation, improving the long-term solderability of metal deposits, ensuring reliable solder joints even under elevated temperatures, and eliminating the need for additional coatings or processing steps.

Problems solved by technology

One issue is long term solderability, defined as the ability of the surface finish to melt and make a good solder joint to other components without defects that would impair the electrical or mechanical connection.
It is relatively easy to achieve 1) and 2), but it is very difficult to achieve 3).
For example, in “two tone” leadframe technology, after the tin or tin alloy plating, the entire package will have to go through many process steps (i.e., a long period of time for such treatments) which require multiple thermal excursions at temperatures as high as 175° C. Inevitably, more and / or thicker surface oxides form, and this in turn reduces the solderability of the tin or tin alloy deposit.
In current processing, it is not possible to omit these additional steps since the final components or assemblies will not be complete.
The first category is undesirable for protection of tin or tin alloy deposits because it introduces an expensive, extra process step.
The second category is also undesirable because it will inevitably introduce impurities onto other critical areas of the leadframe or electrical component due to the non-selective nature of the organic coating that is deposited.
These impurities have proven to be detrimental to the subsequent leadframe and IC assembly processes.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0029] The following electroplating solution was prepared for obtaining a satin / matte tin deposit: [0030] 45 g / l tin as stannous sulfate [0031] 80 g / l sulfuric acid [0032] 15 g / l sodium isotheonate [0033] 5 g / l surfactant [0034] 20 ppm grain refiner [0035] phosphorus source: NaH2PO2 [0036] balance water

example 2

[0037] The following electroplating solution was prepared for obtaining a satin / matte tin-lead deposit: [0038] 63 g / l tin as stannous sulfate [0039] 7 g / l lead as lead methane sulfonate [0040] 100 g / l methane sulfonic acid [0041] 15 g / l sodium isotheonate [0042] 5 g / l surfactant [0043] 20 ppm grain refiner [0044] phosphorus source: NaH2PO2 [0045] balance water

example 3

[0046] The following electroplating solution was prepared for obtaining a bright tin deposit: [0047] 50 g / l tin as stannous sulfate [0048] 80 g / l sulfuric acid [0049] 15 g / l sodium isotheonate [0050] 3 g / l surfactant [0051] 5 g / l brightening agent [0052] phosphorus source: NaH2PO2 [0053] balance water

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Abstract

Methods of providing improved metal coatings or metal deposits on a substrate, improvements in plating solutions that are used to provide such metal deposits and articles of the metal-coated substrates. The solderability of the metal coating is enhanced by incorporating trace amounts of phosphorus in the metal coating to reduce surface oxide formation during subsequent heating and thus enhance long term solderability of the metal coating. The phosphorus is advantageously provided in the metal coating by incorporating a source of phosphorus in a solution that is used to provide the metal coating on the substrate, and the metal coating is then provided on the substrate from the solution.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application is a division of application Ser. No. 10 / 305,547 filed Nov. 27, 2002, the entire content of which is expressly incorporated herein by reference thereto.BACKGROUND ART [0002] The present invention relates to a solution and process for reducing or minimizing surface oxidation of a metal deposit provided by a plating process such as electroplating. The solutions and processes also provide improved deposit properties including appearance and solderability. [0003] Electroplated tin and tin alloy coatings have been used in electronics and other applications such as wire, and continued steel strip for many years. In electronics, they have been used as a solderable and corrosion resistive surface finish for contacts and connectors. They are also used a lead finish for integrated circuit (“IC”) fabrication. In addition, a thin layer of tin or tin alloy is applied as the final step for passive components such as capacitors and tr...

Claims

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Application Information

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Patent Type & AuthorityApplications(United States)
IPC IPC(8): C25D3/00C23C18/44B32B15/01C25D3/56H05K3/24
CPCB32B15/01B32B15/013C25D3/56Y10T428/12715Y10T428/12771Y10T428/12722Y10T428/12708H05K3/244
InventorZHANG, YUNSCHETTY, ROBERT A. IIIHWANG, KILNAM
OwnerTECHNIC INC